Automatic moisture content determination and control apparatus



y 8, 1962 SHINICHI SASAKI 3,034,046

AUTOMATIC MOISTURE CONTENT DETERMINATION AND CONTROL APPARATUS Filed Oct. 12, 1959 BY W W United States AUTOMATIC MOISTURE CONTENT DETERMINA- TION AND CONTROL APPARATUS Shinichi Sasaki, 144 S-chorne, Tokiwa-cho, Urawa City,

Saitama-ken, Japan Filed Oct. 12, 1959, Ser. No. 846,018

3 Claims. (Cl. 324-585) I The present invention relates to an apparatus for determination and control of moisture content in such hygroscopic webs as of fibre, cloth, pulp and other items,

purpose in determining the moisture content in standing-- material. Determination of the moisture content in ma terial during the course of manufacture is essentially liable to considerable errors which are ascribable to such major sources as l) variations of position of the sample relative to the electrodes, (2) changes of dielectric constant of air with relative humidity, (3) variations of the temperature of electrodes, (4) mechanical instability of the position of the electrodes to each other. Any existing method for determination of moisture content on the basis of measurements of resistance or dielectric constant, because of influences from such undesirable factors as stated above does not as yet cease to'show remarkable errors which could hardly be reduced to the minimum. 1

Now, making a point of a microwave phenomenon in which the microwave undergoes sensible attenuation for moisture content in sample, the idea has been to determine the moisture content by turning the attenuation factor of the microwave into moisture contents. According to the present invention, the determination of moisture content in sample on measurements of the microwave attenuation factor has proved as practical as theoretically to be accurate, in case of paper web by simple compensation with the basis weight and temperature measurements as accurately as any existing method. In addition, corrections on compensated measurements are comparatively not only easily made but also errors resulting from such sources as shown above may be reduced to the possible least degree, and the application of an automatic balancing system for microwave attenuation renders laudable sensitivity and stability of operation all thru the time.

One of the objects of the present invention is to provide means that the moisture content in sample should be determined on the knowledge of measurements of the attenuation factor of the microwaves in the waveguide by making a slot, in the direction in which the microwaves proceed or with a certain proper angle, prepared in a part of the waveguide for the moving sample to pass through.

Another one of the objects of the present invention is to provide means that the moisture content determined on the knowledge of attenuation factor of the microwaves in the wave guide should be recorded and that the control of the steam valve, that uses full control over moisture content in smple, should be made by a controller atent 3,934,046 Patented May 8, 196 2 ice is to provide means that not only the moisture content in sample should be brought to knowledge. on the basis of microwave attenuation factor' in the waveguide as shown above, but also a microwave automatic balance to provide means so that the determination of moisture.

content in sample should be'recorded in a potentiometer type recorder. 1

Other objects of the present inven-tion, togetlier with their many advantages they bring, will be clarified in the following description and the accompanying vjdravving, in which: 2 1

. FIGURE 1 is a combination block and schematic diagram of the device contemplated herein; and,

.FlG. 2 is a graphic explanation of the 'wave' .to rrns produced by the device of FIG. 1. 'Referring to the drawing for specific details of the present'invention, electric power supply ES feeds source 1 for oscillator 2, such as klystron and the like, potentiometer type recorder 19, air system automatic cont-roller 20, amplifier 2*1, synchronizing signal amplifier 22 and driving motor 23. Two magic T circuits on both sides 24 and 25 contain comparison waveguide 27 with comparison attenuator 26, the Weight'correction attenuator 28 and the balance attenuator 29. Two attenuators 28 and 29 are coupled across measurement waveguide 4 with a slot d which extends along in the direction in which the microwaves proceed and lets moving sample 5 thru. Theinput circuit has the oscillator '2 and buffer attenuator 3, and at the cross of the magic T circuit 2'4 is placed a transfer shutter 31 which is rotated by a driv ing motor 23 with a permanent rotor 30 afiixe'd on axle. The detector 11, which is placed at end of the output circuit, connects its output circuit with the input one of amplifier 21 which has connection with driving coil 33 forv two-phase motor 32, excitation coil 34 is connected to the output. circuit of synchronizing signal amplifierv 22, the input circuitbeing connected with the both ends of induction voltage coil 36, which, together with the, permanent magnet rotor 30 aflixed on the rotating axle of I driving motor 23, composes generator 35. The rotation of the two-phase motor 32 may make balance'attenuator 29 variable, and is connected with a variable resistance 38 in one of the arms of bridge circuit 37. The bridge circuit 37 is connected with a potentiometer type recorder 19, which is connected with an air system controller 20 for control of the steam control valve 69 prepared in the canal for steam supply for control of moisture content in sample. In the drawing illand 49 show non-reflection terminals, 41 an air supply and 42 a variable resistance for control of sensitivity of the bridge circuit 37. Operation of the example shown above takes place as follows: the source E5 is switched on, the microwaves from the oscillator 2 proceed to be modified to be of proper strength by proper management of the butter attenuator, then to the transfer shutter 31, are divided 7 into two groups to proceed further into the two canals, namely, the comparison waveguide 27 and the measurement waveguide 4- alternately in about 30 c./s.50 c./s.; therefore, the microwaves going into one arm of the magic T circuit 25 thru the comparison attenuator 2/6 and those into another arm of the circuit to go thru the slot a with sample and the balance attenuator 28, al-

" motor 23 which operates the transfer shutter 31.

. U I ternately reach the detector [1. When new such microwavesas shown above alternately proceedthru the two canals in two groups,]are so managed to hold balance with themselves by regulating the comparison attenuator 27, the output' wave ,forms'of the amplifier'll and the de-' tection outputof the detector h present such wave forms as shown inA and B of FIG. 2 and the two-phase motor 32 keepsstandstill. But, when the moisture content in sample moving thru the slot d changes and correspondingly the attenuation vfactor of themic'rowaves in the -m'easurenrent Waveguide 4 changes, balance between those microwave groups in the two waveguides -27 and 4- is" lost. The Wave form of the detection output in this momentof the detector 11 and that of the output of the amplifier 21 are as shown in C and D, of FIG. 2; the synchronizing frequency portion of the wave fonm of the latter manifests such appearance as shown by a dotted line and consequently, phase'dilference is produced with the waveformsof the output of the synchronizing signalv amplifier 22, the synchronizing signal itself being induced in the induction voltage coil 36 by the rotation of the rotor: 30 afiixed on the rotary' axle of the driving The twQ-Phase motor 32 beginsfto rotate with its driving coil 33 being connected withthe outpufcircuit' of the am pIifienZiand its exciting coil 3-4. with the output circuitof the synchronizing signal amplifierll, and" the interlock- :f .ing balancenttenuator 29'works and the two-phase motorv i 32 not; come to standsn'll until the two groups of *microwaves from the twowaveguides 29 and 4 come to a balance. The two-phase imotor: rotates, i.e. in proportionto the change introduced in the moisture content in ture content. in a sample which moves through the do vice, comprising in combination: a microwave oscillator 4 the two-phase motor, enables the catching of any weakest change in moisture content in the sample and realizes rneasurementexpressive of high sensitivity, accuracy and stability, almost perfectly tree from such special influence as should come from furnish, pH, density, basis Weight, thickness, ash-contents, and so on in the sample.

it is clear that the apparatus of the present invention is also able to measure to determine any variation in web. P density, of any part ofa moving. sample thru the waveguide, should moisture contentinsample be held to stand at a certain definite value.

What is claimed:

1. A 'crowave device for determination of the-moisfed bya power source; a first attenuator fed by said oscillator to maintain waves produced by said oscillator in a waveguide network; a finst magic-T circuit coupled to said attenuator dividing the output from said attenuator; into two parallel branches; a'rotatablejtransfer shutter at the cross point of said 'magic-T including: driving means therefor; a measuring waveguide fed by said first parallel branch at one end, having a longitudinal straight portion sample 5. The rotating axle 'of'the two-phase motor 32 e I is connected with the variabie resistance 38 in one of the armsoilthe bridge circuit 37, and the rotary angleof the rotating axle is turnedinto phase difference, and recording is made by the potentiometer type. recorder. The control of the steam control valve by working an air systom automatic controller 2 corresponding to indications by-the recorder makes it feasible to make an automatic and uninterrupted production of samples of definite nloisture contents by providing samples with steam. sup; ply correcting deviations .from the prescribed band ofmoisture content in sample.

Said example has it too that the determination of the ,moisture contentin the sample is made on the basis 'of the attenuation factor of the microwave affected'by the moving sample thru the slot prepared in the'waveguide.

Application however to the use of an automatic balance circuit for microwaves as shown above, neutralizes possible output fluctuations for fluctuating source volt-age or temperature of the oscillator, klyst-ron and the like gives not only high stability in any unit operation, but also indications of remarkable accuracy, should a high ipertorm'ance variable resistance be used in the bridge circuit. Adoption of the synchronizing detection system which gives synchronizing signal and waveguide output to extending from said fed endya recessed section in said longitudinal straight portion forming a slot in said measuring Waveguide for passage of a sample therethrough; a comparison waveguide fed by said second parallel branch atone end; second and third attenuators in said measuring and comparison waveguide circuits; a magic-T circuit-fed by the outputs of said measuring and comparison waveguide circuits including output means combining the outputs of said measuring and comparison waveguide circuits; a detector at the end offsaid output means; motor means responsive to said detector output and said rotatable transfer shutter driving means; a bridge circuit responsive to said motor means; and, indicator mean responsive to saidbridge circuit.

2. A device as claimed in claim 1, including recorder means responsive to said bridge circuit.

3. A device as claimed in claim 1, including steam control valve meansresponsive to, said bridge circuit.

' ReEerences Cited in the file of this patent UNITED STATES PATENTS 

